The present invention relates to an apparatus for charging a plastic mass into the hollow interior of a capsule or magazine. More particularly this invention concerns an apparatus for injecting dental amalgam into a filling instrument as described in my above-cited copending applications.
My above-cited patent applications, which correspond to German published specification No. 2,364,547, describe a dental appliance for introducing filler material into a tooth cavity. This appliance comprises an elongated support carrying at one end a discharge nipple having elongated interior channels formed with an outlet opening transversely of the support, an inlet opening longitudinally of the support, and a lateral opening intermediate the inlet and the outlet and itself opening longitudinally of the support. Means is provided in the support forming a passage having an open end directed generally longitudinally of the support toward the nipple and in line with the lateral opening. A replaceable capsule or magazine is engageable between the open end and the lateral opening and has a throughgoing chamber adapted to hole a body or mass of the filler material and open to the open end and to the lateral opening. A first expelling element is reciprocal through the passage and the chamber. A first piston is carried on this first element. A first cylinder is provided in the housing surrounding the first piston and subdivided thereby into a front compartment and a rear compartment. First a valve means is effective in a first position for feeding air under pressure into the rear compartment and thereby advancing the first element through the chamber to push material therein into the channel through the lateral opening and effective in a second position to withdraw the element from the chamber into the passage. A second expelling element is formed as a flexible wire having a tip reciprocal in the passage past the lateral opening. A second piston is carried on this second element. A second cylinder is provided in the housing surrounding the second piston and subdivided thereby into a front compartment and a rear compartment. Second valve means is effective in one position for supplying air under pressure to the rear compartment of the second cylinder to push the tip in the channel past the lateral opening toward the outlet and effective in another position for withdrawing the tip away from the outlet past the lateral opening.
Such a device serves to inject the amalgam mixture into a tooth cavity. Further such devices are described in German published specification No. 1,491,002, British Pat. No. 934,235 and U.S. Pat. Nos. 3,623,224 and 3,638,314. U.S. Pat. No. 3,751,807 as well as my above-cited copending applications describe such a system wherein the entire filling apparatus need not be taken out of use during filling, as such devices have a removable capsule or magazine which can be separated from the apparatus and then filled. This system allows the dentists technician to fill extra magazines or capsules while the dentist himself or herself is filling the tooth.
It is necessary to prepare an amalgam mixture, normally comprising by weight 65% silver, 25% tin, 6% copper, 2% zinc, 3% mercury and traces of gold and platinum. Such a standard amalgam mixture remains plastic for between 5.0 and 10.0 minutes after it is mixed up, and hardens completely after approximately 2.0 hours. It is therefore necessary to combine the ingredients, mix them, load the filling device, inject the mixture into the cavity with the filling device, and shape and tamp the filling thus formed within 5 or 10 minutes. It is possible to speed the mixing time by using a vibrating amalgamator that insures almost instantaneous mixing of the above-mentioned ingredients. The bottleneck in the operation typically lies in transferring the ready-to-use mixture to the filling appliance. No practical solution has yet been presented to speed this operation.